Overshot fishing tool



Manila 9, 1943.-

Filed May 24, 1941 2 Sheets-Sheet 1 A l l INVENTOR ATTORNEY Patented Mar. 9, 1943 UNITED STATES PATENT OFFICE OVERSHO-T FISHING TOOL Philip M. Rea, Oklahoma City, Okla.

Application May 24, 1941, Serial No. 395,049

4 Claims.

The invention relates to fishing tools for engaging and removing broken drill pipe, and the like, from wells.

In rotary oil well drilling, it is becoming a general practice to use smaller diameter Well casing, due to the increased depth of many present day wells, but it has been found that the drill stem cannot be materially reduced in diameter without weakening it to such an extent that it becomes twisted off in the well. The result is that overshot fishing'tools must now be so designed that they will operate successively in a confined annular space between the fish and the well casing. This means that the thickness of the overshot housing or bowl and of the segmental pipe slips must both be materially reduced, thus causing a reduction in the lateral thickness of the usual tapered slip seating surface formed in the bore of the bowl.

The reduction in the lateral thickness of the slip seat and in the thickness of the slips has presented a problem which the present invention is primarily designed to overcome. This problem consists of dihiculty in keeping the lower ends of the slips pressed outwardly against the bowl wall, so that they will not slide downwardly on their seat and foul with the fish as the bowl passes downwardly thereover.

It is therefore the prime object of the present invention to provide, in a slip type overshot, a positive means for preventing the lower ends of the slips from'projecting inwardly into the path of a fish which is entering the overshot bowl.

Overshot fishing tools of the circulating type are usually provided with a resilient or compressible annular packing sleeve for sealing between the inner wall of the overshot bowl and the outer surface of the fish, after the fish has entered the bowl. This is done in order to permit circulation of fluid through the fish.

Before the advent of the thin-walled bowl, the outer surface of the packing sleeve could be, and was usually, confined in an annular groove formed in the wall of the bowl, and the packing sleeve could therefore have asufficient wall thickness or body to successfully span the space between the bowl and the fish through deformation, and the packing sleeve could also have a sufiiciently large bore to insure free entry of the fish thereinto without danger of the sleeve being fouled and destroyed by movement of the fish therethrough.

With the'reduction in thickness of the bowl and'slips; it has been necessary'toalso reduce the wall thickness or body of the packing sleeve. This has presented the following described difiiculties: If the packing sleeve is formed with a central bore of sufficient diameter, in its normal shape, to insure .free passage of the fish therethrough, there is insufficient material in the thin-walled sleeve to successfully fill the annular space between the fish and the bowl, and a positive seal is thus unattained. 6n the other hand, if the bore of the packing sleeve is made smaller than the outer diameter of the fish, in order to obtain sufiicient body, it fouls with the fish and is usually sheared oil or destroyed by the-fish as the bowl-moves downwardly thereover.

It is consequently another important object of the present invention to provide, in an overshot fishing tool, an arrangement of parts which permits the use of a packingsleeve having a bore normallyof smaller diameter than that of'the fish, and in which means is provided for preventing the sleeve from becoming damaged as it passes downwardly over the fish.

Other objects will be apparent from the following description when taken in connection with the accompanying two-sheet drawings wherein:

Figure 1 is an elevational sectional view of an overshot fishing tool embodying the present invention, and'show-ing the fish entering the slips;

Figure 2 is an elevational view, partially in vertical section, of a traveling sleeve which constitutes the major portion of the invention;

Figure 3 is' an elevational sectional view of the tool with the fish within the slips andthe traveling sleeve moved partially upward in the bowl j and,-

Figure 4 is a View similar to Figure Sshowing the fish after it has moved entirely through the slips and packing sleeve, and after the entire fishing tool has been moved upwardly a sufficient distanceto cause the slips to fricti'onally engage Like characters of reference designate like parts in all of the figures wherein they occur.

Intermediate its and inwardly tapered slip seat 4 adapted to slideably seat a set of usual segmental pipe slips 5, normally provided on their inner surfaces with screw threads 6.

It is common practice in the art to provide an annular resilient packing sleeve I within the bowl 2 adjacent the upper ends of the pipe slips 5, and it is also common practice to provide above said sleeve I a compression spring 8 for urging the sleeve and slips downwardly upon the seat 4. In the embodiment shown in the drawings, the upper end of the spring 8 is adapted to seat beneath the lower end of the pipe section I to which the bowl 2 is threadedly attached; any desired abutment may be provided for this purpose, however.

It may readily be understood that in the structure thus far described there is nothing provided to prevent downward movement of the slip segments upon the slip seat 4 due to the action of the spring 8. Such a movement would normally cause the lower ends of the slip segments to pro- J'ect inwardly beyond the wall of the bore 9 of the bowl 2. If this were permitted, it may readily be seen that when the bowl is lowered over a fish, which in the drawings is indicated by the reference numeral Ill, the upper end of the fish would be prone to engage the lower ends of the slip segments. In cases in which the slips have thin walls, it has in the past been found that the slips are often broken by such contact with the upper end of the fish.

As previously described hereinabove, a packing sleeve such as has heretofore been commonly used, and which has a wall thickness substantially equal to the thickness of the slips, is so thin that even after a fish has passed therethrough there is insufficient body deformation ofthe sleeve to effect a proper seal between the fish and the upper wall of the bowl 2. It may also be seen that if the wall thickness of this sleeve were to be increased in order to accomplish the proper sealing ofiilce, the inner surface of the sleeve would project into the path of the fish, and would thus be subject to becoming sheared off. In the present embodiment, the packing sleeve I is normally of a thickness greater than the thickness of the slips 5, and therefore a means must be provided for protecting the sleeve 1 against destruction by contact with the upper end of the fish.

As a means for holding the slip segments outwardly within the confines of the slip seat 4, and also as a means for holding the packing sleeve I expanded out of the path of the fish, there is provided a traveling metal sleeve II which is best illustrated in Figure 2. This traveling sleeve II consists substantially of a preferably solid tubular element having a smooth inner bore and having an outer circumference at its lower end portion I2 substantially equal to the outer diameter of the fish I0. The sleeve II has an upper outer portion I3 which is reduced in diameter from that of the lower portion I2, and intermediate the portions I2 and I3 the outer surface of the sleeve II is gradually tapered inwardly and upwardly as shown at I4.

The upper end of the sleeve II has an annular downwardly facing abrupt shoulder I5, and when the sleeve is operatively installed in the bowl 2, the shoulder I5 rests upon the upper end of the packing sleeve I with the portion l3 extending through the sleeve. The lower portion I2 of the sleeve II normally resides within the slip segments 5 and acts as 'a means for holding the slips at the upper end of their permitted travel and outwardly against the inner wall of the bowl 2. The slips 5 and packing sleeve I are consequently held in extended positions which causes them to remain outside of the path of the fish III as it enters the lower end of the bowl 2. This normal position of the slips 5, resilient sleeve 1, and traveling sleeve II, is shown in Figure 1.

Operation In operation, as the bowl 2 is lowered over the fish III the fish is free to first enter the slips 5 to the position shown in Figure 1. Further downward movement of the bowl 2 causes the traveling sleeve II to be contacted by the upper end of the fish which forces it to move upwardly in the bowl 2, as illustrated in Figure 3, and this upward movement causes the tapered portion I4 of the sleeve II to compress the resilient packing sleeve 1 outwardly against the wall of the bowl 2. Further downward movement of the bowl 2 over the fish causes the traveling sleeve II to be moved upwardly out of the slips 5, thus permitting the slips to slide downwardly upon the seat 4 into a position to frictionally engage the outer surface of the fish I0. Still further downward movement of the bowl 2 causes the traveling sleeve II to pass upwardly out of the resilient packing sleeve I. thus permitting the packing sleeve to contract, through its inherent resiliency, and to thus contact the periphery of the fish. During this movement the sliding sleeve II is traveling upwardly within the compression spring 8 which is of a sufiicient internal diameter to allow this passage.

As soon as the traveling sleeve I I is forced upwardly out of the slips 5 and out of the packing sleeve I, the spring 8 is free to urge the sleeve I and slips 5 downwardly. After this has happened, should a fluid under pressure be injected into the pipe string I, the fluid will contact the upper end of the resilient sleeve I and deform or distort it into a positive sealing contact with the periphery of the fish and with the inside surface of the bowl 2, and consequently, circulation through the fish I0 is attained.

From the above description, it will be apparent that all possibility of the slips 5 or of the packing sleeve 1 becoming fouled with the upper end of the fish is eliminated, and since the slips can not contact the fish until after the traveling sleeve I I has been forced out of them, there is no possibility whatsoever of the slips becoming destroyed by the fish.

It will also be apparent that since the resilient packing sleeve I is held out of engagement with the fish until the fish has actually entered the bore thereof, the fish can not then act to but it may be found desirable to use the traveling sleeve I I in combination with any and all types of pipe slips, and I therefore do not wish to confine myself to the use of --the traveling sleeve principle in connection with only a certain type of pipe slips. It is further contemplated that in many instances the traveling sleeve II will be used in.overshot bowls of the non-circulating type wherein no packing element, such as the sleeve 1, is provided.

It will be apparent that should the spring 8 be eliminated from the structure illustrated in the drawings, the sealing sleeve 1 would likely travel upwardly in the bowl 2 along with the traveling sleeve l I. In this event, when the fluid pressure is injected into the pipe string I, the downward pressure upon the upper end of the sleeve It and also upon the upper end of the resilient sleeve 1, will force the two sleeves to travel downwardly until the sleeve I I contacts the upper end of the fish l0, thereafter, this fluid pressure will then act to distort or deform the sleeve '1 to accomplish its sealing ofice.

Obviously, other means than a solid sleeve could be used within the slips and within the packing sleeve to hold the two extended so that they may properly receive the fish. For instance, the sliding sleeve Il could be replaced with radially spaced vertically extending bars, or their equivalent, which are held in any desired manner in their spaced relation.

It is also obvious that separate sleeves could be furnished, one originally residing within the slips, and the other within the packing sleeve. Further, it may be found desirable to use a sliding sleeve only within the packing sleeve, or only within the slips. The word slips as used herein is intended to mean, broadly, any pipe grappling means operating to engage a fish through action upon a tapered surface.

It is also apparent that in overshots having resilient packing elements below the pipe grappling elements, the sliding sleeve will function with equal efficiency, and in substantially the same manner, as illustrated in the drawings and described hereinabove. In such cases, the tapered portion Id of the sleeve H may be eliminated. It may also be found desirable to dispense with the tapered portion l4 when the sleeve II is being used in overshots of the type illustrated in the drawings herein.

I claim:

1. In an overshot fishing tool, the combination with a rigidly constructed hollow housing or bowl having a tapered slip seat formed therein, segmental pipe slips within the bowl and seated upon said slip seat, and with a resilient annular packing element in said bowl and rsting upon said slips, of: a tubular non-compressible sleeve having both ends fully open, said sleeve normally retained slidably within the slips and within said packing element and normally acting to hold the two outwardly against the wall of the bowl, saidsleeve being adapted to be moved upward in the bowl out of said slips and out of the packing element by the contact of a fish which is ntering the lower end of the bowl.

2. In an overshot fishing tool, ;the combination with a rigidly constructed hollow housing or bowl having a tapered slip seat formed therein, segmental pipe slips within the bowl and seated upon said slip seat, a resilient annular packing element in said bowl and resting upon said slips, and with a spring for exerting downward pressure upon said packing element and slips, of: a tubular non-compressible sleeve having both ends fully open, said sleeve normally retained slidably within the slips and within said packing element and acting when so retained to hold the packing element and slips outwardly against the wall of the bowl, said sleeve adapted to be moved upwardly out of said slips and out of the packing element by the contact of a fish which is entering the lower end of the bowl.

3. In an overshot fishing tool, the combination with a rigidly constructed hollow housing or bowl having a tapered slip seat formed therein, segmental pipe slips within th bowl and seated upon said slip seat, a resilient annular packing element upon the top of said slips, and a spring exerting downward pressure upon said packing element, of: a tubular non-compressible sleeve having both ends fully open, said sleeve normally residing within said packing element and normally holding the element expanded outwardly against the wall of said bowl, said sleeve adapted to be moved upwardly out of said packing element by the contact of a fish which is entering the bowl from below.

4. In an overshot fishing tool,.the combination with a rigidly constructed hollow housing or bowl having a tapered slip seat formed therein, segmental pipe slips within the bowl and seated upon said slip seat, a resilient annular packing element upon the top of said slips, and a spring exerting downward pressure upon said packing element, of: a tubular non-compressible sleeve having both ends fully open, said sleeve normally residing within said packing element and normally holding the element against collapse by the spring'and expanded outwardly against the wall of said bowl, said sleeve adapted to be moved upwardly out of said packing element by the contact of a fish which is entering the bowl from below.

PHILIP M. REA. 

